The present invention relates to a brake system used for a vehicle.
The following brake apparatus (brake system) is described in JP 2008-239142 A. The brake apparatus includes: a master cylinder for generating a brake hydraulic pressure; an anti-lock brake system provided between the master cylinder and a wheel cylinder; and an electric booster including an input member moving forward and backward in response to an operation of a brake pedal and an assist member moving forward and backward by being driven by an electric actuator. The electric booster generates a boosted brake hydraulic pressure in the master cylinder under an input thrust applied to the input member from the brake pedal and an assist thrust applied to the assist member by the electric actuator. Then, the electric booster transmits a part of a reactive force generated by the brake hydraulic pressure to the input member and another part of the reactive force to the assist member.
In the brake apparatus described in JP 2008-239142 A, a control origin position for the assist member, and consequently the control origin position used by control means to perform control needs to be determined for the control at the time of system start-up or the like.